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Comparing Reef Fish Habitat Use Patterns In and Out of Hawaiian Marine Protected Areas

Project Status: This project began in October 2003 and was completed in December 2010

Coral reefs are key habitats for many near-shore Hawaiian fishes. Marine protected areas (MPAs) are created to provide islands of protection for species, habitats, and ecosystems with high species diversity and abundance. This study was done to document how Hawaiian reef fish species use different seafloor habitats and to determine if and how well the MPAs are conserving the species.

Why We Care
Coral reefs are key habitats for many Hawaiian fishes. The fishes of Hawaii play critically important economic and cultural roles, and their protection is a high priority among the people of Hawaii.

Determine the effectiveness of primary Hawaiian Island MPAs under various management approaches

Make recommendations to Hawaii’s Department of Land and Natural Resources on the effectiveness of existing MPAs and suggest additional areas for protection based on species habitat requirements.

We developed digital seafloor maps for selected coral reefs in Hawaii and monitored how reef fish used those habitats. We combined the spatial distribution data of seafloor coral habitats and fish species use of those habitats; this approach identified the patterns of how species use or prefer various habitat types and locations. This “integrated seascape ecology” method is useful in quantitatively defining essential fish habitat and defining biologically relevant boundaries of marine protected areas. These integrated products of species and habitat are being used to help resource personnel make informed management decisions.

A science-based assessment of the effectiveness of Hawaii's MPA system was done, supporting the federally mandated MPA and essential fish habitat initiatives. This approach not only helped resource managers in Hawaii evaluate existing MPAs and design new protected areas, it also laid the groundwork for broad-scale comparisons throughout the Hawaiian archipelago, the U.S. Pacific, and the U.S. Caribbean.

What We Found
Over the past four decades, Hawaii developed a network of 11 marine life conservation districts (MLCDs) to conserve and replenish marine resources around the state. These MLCDs varied in size, habitat quality, and management approaches, which provided an excellent opportunity to tests hypotheses concerning MPAs’ design and function using multiple discrete sampling units.

Results of our work showed that MPAs had higher values for most fish assemblage characteristics (e.g., total concentration, size, diversity) compared with adjacent control areas across all habitat types. In addition, top predators and other targeted resources species were more abundant and larger in the MLCDs, illustrating the effectiveness of these closures in conserving fish populations. Habitat complexity, quality, size, and level of protection from fishing were important determinates of MLCD effectiveness with respect to their associated fish populations. If protective areas are to be effective, they must include the diversity of habitats within the entire ecosystem to accommodate the wide range of species under consideration.